The present invention relates generally to optical image scanning and, more particularly, in a flat plate scanner utilizing manual document feed and also having an automatic document feeder, the use of a single sensor for detecting both a leading edge of an original document input via the automatic document feeder and the opening of the flat plate top cover.
Automated business machines for producing or reproducing hard copy documents, such as copiers, printers, telecommunications facsimile and digital sending machines, document scanners, multi-function devices (MFD), and the like, are well-known commercially. Ideally, when working with cut sheet print media, a copying or optical scanning apparatus will provide both manual document feed and automatic document feed capabilities. Often such apparatus include an automatic document feeder (ADF) mechanism for automatically loading and unloading single sheets sequentially to a functional station where the apparatus performs an operation, e.g., sequentially scanning the fed document sheets for copying, faxing, displaying on a computer monitor, or the like. Following the operation, the ADF then off-loads a sheet and feeds the immediately following sheet of the document to the functional station. A sequential flow of sheets by the ADF and positioning without the necessity of manual handling reduces the time required to accomplish the complete functional operation.
Optical scanners operate by imaging an object (from a sheet of paper, document or other form of medium) with a light source, sensing a resultant light signal with an optical sensor array. Each optical sensor in the array generates a data signal representative of the intensity of light impinged thereon for a corresponding portion of the imaged object. The data signals from the array sensors are then processed (typically digitized) and stored in a temporary memory such as a semiconductor memory or on a hard disk of a computer, for example, for subsequent manipulation and printing or display, such as on a computer monitor. The image of the scanned object is projected onto the optical photo sensor array incrementally by use of a moving scan line. The moving scan line is produced either by moving the document with respect to the scanner optical assembly, or by moving scanner optical assembly relative to the document. Either or both of these methods may be embodied in flat bed scanners, hand held scanners, or any scanner having manual and automatic feed capabilities.
Various types of photo sensor devices may be used in optical scanners. For example, a commonly used photo sensor device is the charge coupled device (CCD). A CCD builds up an electrical charge in response to exposure to light. The size of the electrical charge build up is dependent on the intensity and the duration of the light exposure. In optical scanners, CCD cells are aligned in linear array. Each cell or xe2x80x9cpixelxe2x80x9d has a portion of a scan line image impinged thereon as the scan line sweeps across the scanned object. The charge built up in each of the pixels is measured and discharged at regular xe2x80x9csampling intervals.xe2x80x9d In most modern optical scanners, the sampling intervals of the CCD arrays are fixed.
As previously mentioned, an image of a scan line portion of a document is projected onto the scanner""s linear sensor array by scanner optics. In CCD scanners, the scanner optics include an imaging lens which typically reduces considerably the size of the projected image from the its original size. Pixels in a scanner linear photo sensor array are aligned in a xe2x80x9ccrossxe2x80x9d direction, i.e., a direction parallel to the longitudinal axis of the scan line image which is projected thereon. The direction perpendicular to the xe2x80x9ccrossxe2x80x9d direction will be referred to herein as the xe2x80x9cscanxe2x80x9d direction (i.e., paper or sensor linear array movement direction for scanning of the image).
At any instant when an object is being scanned, each pixel in the sensor array has a corresponding area on the object which is being imaged thereon. This corresponding area on the scanned object is referred to herein as an xe2x80x9cobject pixelxe2x80x9d or simply xe2x80x9cpixel.xe2x80x9d An area on a scanned object corresponding in area to the entire area of the linear sensor array is referred to herein as an xe2x80x9cobject scan linexe2x80x9d or simply xe2x80x9cscan line.xe2x80x9d For descriptive purposes, a scanned object is considered to have a series of fixed adjacently positioned scan lines. Further, scanners are typically operated at a scan line sweep rate such that one scan line width is traversed during each sampling interval.
Differentiating from scanners employing CCDs, a contact image sensor (CIS) and CIS drive roller are commonly employed in document fed scanners for imaging the medium being passed (fed) through the scanner. The CIS is spring loaded against the drive roller and forms a nip therebetween. The medium being scanned is presented for scanning at the nip and is pulled past the CIS by the drive roller. The CIS typically includes a glass plate adjacent the roller (forming the nip), an array of light sources, such as light emitting diodes (LEDs), directed at the nip, an array of self-focusing lenses (cylindrical microlenses) that direct and focus the light from the light sources as reflected off the medium (or roller if no medium is present), and an array of photo sensors adjacent the self-focusing lenses for converting the light passed through the lenses to electrical signals for processing of the image generated. An advantage of the CIS is that it is less susceptible to having foreign particles (e.g., dust) settle on the CIS optics which could degrade the scanned image quality. A CIS is less susceptible to foreign particles because it has fewer reflecting optics, relative to CCD scanner devices, for focusing the light. Another advantage of the CIS is its small size due to its optical configuration.
It is known to provide a single plate flatbed scanner including an automatic document feeder which automatically feeds documents page by page. Each document fed into the ADF is conveyed to a scanning point or portion of the flat plate where the document is scanned by an image sensor and then the document is conveyed to a point outside the ADF, such as a document output tray. Typically, the image sensor remains fixed at the scanning point xe2x80x9creadingxe2x80x9d or scanning the image as the document is conveyed past the scanning point by the ADF. Another feature of the flatbed scanner allows a user to manually place or position an original document on the flat plate to be scanned. The document lays flat on and covers a portion of the flat plate while the image scanner is moved under the plate the length (or width) of the document to read or scan the document. In many flatbed scanners, the scanning point or portion of the flat plate used to scan a document provided by the ADF is separate and distinct from the portion of the flat plate utilized to scan a document manually positioned on the plate.
In some flatbed scanners, in order to reduce the size of the flat plate (and the overall size of the scanner), it is also known to utilize a portion of the flat plate for the scanning point for documents fed by an ADF (xe2x80x9cADF scan windowxe2x80x9d) which also forms a part of the flat plate portion for scanning documents manually positioned on the plate. However, a document manually placed on the plate will typically cover the entire plate including the ADF scan window. Thus, if a manually-placed document has been inadvertently left on the flat plate when a user attempts to scan a document using the ADF, the ADF scan window will be blocked, i.e., covered, and the ADF fed document will not be scanned. For this reason, many scanners, especially those used in multifunction devices, will employ a sensor to detect opening of the flat plate lid or cover.
Automatic document feeders typically also utilize sensors for detecting a leading edge of a document as it is withdrawn from an input or supply tray and fed into the scanner. From the point in time that the leading edge is detected, the amount of time required to convey the leading edge to the imaging sensor is monitored so that the imaging sensor may initiate actual imaging (scanning) at the precise time when the leading edge of the document reaches the imaging sensor. This amount of time will be more or less depending on the relative location of the sensor, or sensors, in the ADF document feed path.
Thus, a flatbed scanner employing an ADF may have at least two sensors, one to detect a document leading edge and one to detect the opening of the flat plate lid or cover. In order to reduce cost and component numbers, what is needed is a way to eliminate one or more of the presently used sensors yet maintain the required functionality.
In a preferred embodiment, the present invention is implemented in a single plate flatbed scanner including an automatic document feeder (ADF) which employs a single sensor to detect both a document leading edge for an ADF fed document and the opening of the flat plate cover. At least one sensor is eliminated thus reducing the number of components and the cost of manufacture while continuing to provide desired functionality.
A preferred embodiment of a flatbed scanner according to the present invention providing both automatic and manual document input includes a single contact glass plate mounted on a main body. The contact glass plate defines a flatbed scanning area where an original document may be manually positioned. Additionally, an ADF scan window where ADF-fed documents are scanned is defined within the flatbed scanning area. An image sensor assembly, such as a CCD sensor or a CIS sensor, for example, is maintained at a fixed position under the glass plate in the ADF scan window while scanning ADF-fed documents. To scan a manually fed document, the image sensor assembly moves under the flatbed scanning area so as to scan an image of the document manually positioned on the glass plate. An automatic document feeder is arranged on the main body covering the contact glass and mounted to be openable to expose the contact glass to allow the manual placement on the flatbed scan area of a document original to be scanned. The automatic document feeder conveys an original document to be scanned along a feed path to the ADF scan window at the image sensor assembly fixed position, conveying the original document over and past the image sensor assembly and ejecting the original document along an ejecting path from the fixed position. The scanner of the present invention includes a detector adapted both to detect when the automatic document feeder is opened and to detect a leading edge of an original document whenever a document page is conveyed along the feed path to the ADF scan window.
In a preferred embodiment of the present invention, an optical switch is operatively mounted on the ADF and detects both the leading edge of an ADF fed document page and the opening of the ADF to expose the surface of the contact glass plate. Preferably, the optical switch provides a light beam which is interrupted by a swing arm to generate an electrical signal. The optical switch and swing arm are mounted such that one end of the swing arm projects into the ADF feed path to operatively engage each sheet or page of an ADF fed document to generate an electrical signal indicative of the leading edge of a page prior to the document page reaching the image sensor fixed position in the ADF scan window. The optical switch and swing arm are mounted to additionally operatively cooperate with the scanner main body to generate an electrical signal indicative of the opening of the ADF to expose the contact glass plate.
Other embodiments and advantages of the present invention will be readily appreciated as the same become better understood by reference to the following detailed description, taken in conjunction with the accompanying drawings. The claims alone, not the preceding summary or the following detailed description, define the invention.